Printing devices that print images by ejecting dots on a print medium are in widespread use. Some such printing devices employ an interlaced printing method known in the art in which dots are formed on adjacent main scanning lines in different main scans. Using interlaced printing, a printing device can print at a higher resolution, whereby the pitch of dots in the sub-scanning direction (the line spacing of adjacent main scanning lines) is smaller than the nozzle pitch in the sub-scanning direction.
There exists in the art a technology for expanding a printing region in which interlaced printing can be performed while ensuring the precision for conveying a print medium (sub scan precision). Specifically, the technology switches the printing method from a method that uses a large conveying distance to convey the print medium to a method that uses a small conveying distance at a timing approaching the point that the print medium transitions from a state held both by paper-supply rollers (upstream-side rollers) and by paper-discharge rollers (downstream-side rollers) of the conveying mechanism (hereinafter referred to as a double-clamped state) to a state in which the end of the print medium separates from one of the roller pairs (the paper-supply rollers; hereinafter referred to as a single-clamped state). This enables the device to expand the printing region within which printing can be performed in a double-clamped state. Note that dots have already been formed in main scan lines through previous main scans for which dots can be formed in main scans after the printing method was switched.